Extract from CWGC site (see link)
The notorious Burma-Siam railway was a Japanese project driven by the need for improved communications to support the large Japanese army in Burma.
It was built by a slave labour force of Commonwealth, Dutch and American prisoners of war, and civilians drafted from countries occupied by the Japanese.
During its construction, approximately 13,000 prisoners of war died and were buried along the railway. An estimated 80,000 to 100,000 civilians also died in the course of the project, chiefly forced labour brought from Malaya and the Dutch East Indies, or conscripted in Siam (Thailand) and Burma (Myanmar).
Two major groups of workers began at opposite ends of the line towards the centre. The Japanese aimed at completing the railway in 14 months and work began in October 1942. The line, 424 kilometres long, was completed by December 1943.
The graves of those who died during the construction and maintenance of the Burma-Siam railway (except for the Americans, whose remains were repatriated) that could be located, were transferred from camp burial grounds and isolated sites along the railway into three cemeteries at Chungkai and Kanchanaburi in Thailand and Thanbyuzayat in Myanmar.